This study may answer or shed considerable light on three questions of great interest to the Institute and to all those in heart research. 1. Is angiography a reliable and useful tool for evaluation of coronary artery disease? Can changes on angiography be read reliably enough to serve as an endpoint for scientific studies or important clinical decisions? 2. Can we significantly decrease the incidence of M.I. or death without any additional new treatments or medications? 3. Will lowering cholesterol slow down, stop, or reverse the progression of coronary artery disease?